Crossfire MAP sensor / High Rev Help
Thread Starter
Intermediate
Joined: Jan 2009
Posts: 34
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From: Albany Western Australia
Crossfire MAP sensor / High Rev Help
82 Collectors Edition Crossfire.
I had prev asked for help with questionable ECM fault.
After hours of work, I finally found no ECM fault.
My MAP sensor vacuum hole was 3/4 blocked with what looked to be white grease. Checked voltage etc, and TPS ohms, all correct.
Car has been flooding on cranking engine. After cleaning hole in MAP sensor, car finally started, and ran.
The revs are now higher than should be, idle at 1500. Is this the MAP, or something else. I may be wrong but it may have been higher than normal before it broke down.
Any help appreciated. Richard, Western Australia
I had prev asked for help with questionable ECM fault.
After hours of work, I finally found no ECM fault.
My MAP sensor vacuum hole was 3/4 blocked with what looked to be white grease. Checked voltage etc, and TPS ohms, all correct.
Car has been flooding on cranking engine. After cleaning hole in MAP sensor, car finally started, and ran.
The revs are now higher than should be, idle at 1500. Is this the MAP, or something else. I may be wrong but it may have been higher than normal before it broke down.
Any help appreciated. Richard, Western Australia
Le Mans Master
Joined: Jul 2000
Posts: 6,663
Likes: 162
From: columbia city in
flooding on start,iwould check the coolant sensor in front by the water pump.and then check your tps switch [throttle postion switch]see if it is operating smoothly.high rpm sounds like a vac leak check all around the intake .check all hoses .
Melting Slicks
Joined: Jul 2005
Posts: 2,740
Likes: 3
From: Aurora Ontario
Richard,
Make sure the white grease didn't gum up the MAP sensor. Sounds like you are getting close. As Terry indicated the CTS is important as well as the TPS. Those three plus the O2 is what the ECM uses to determine fuel/air mixture and idle.
Remember its not a carb. For the idle to be 1500 the ECM is telling it to be that. For it to be 1500 the ECM thinks the engine is cold or the TPS is saying the car is doing 20 kph or the MAP is saying I'm about to stall (low Manifod pressure) so send more gas. You need to figure out which of the three it is. Explanation is crude but somewhat accurate.
You also need to make sure the IAC's are cycling. Take the cleaner off. Start it. Let it go to 1500. While you are at it disconnect the hose on the rear of the intake that feeds the headlights and plug it. You may have a leak in the headlight system. Also unplug the hose that goes to the master cyclinder and plug it at the manifold...the valve the hose attaches to at the master cylinder sometimes fails causing a vac leak. Anyway once its running. Give it a bit of gas...look down the hole to the driverside of the TBI's its right infront of where the IAC's screw in...do you see a pin moving in and out? You should this adjusts the air flow into the TBI's and are controlled by the ECM. I also assume you are plugging the hose that comes out of the rear TBI and goes to the aircleaner when you remove it.
Jim
Make sure the white grease didn't gum up the MAP sensor. Sounds like you are getting close. As Terry indicated the CTS is important as well as the TPS. Those three plus the O2 is what the ECM uses to determine fuel/air mixture and idle.
Remember its not a carb. For the idle to be 1500 the ECM is telling it to be that. For it to be 1500 the ECM thinks the engine is cold or the TPS is saying the car is doing 20 kph or the MAP is saying I'm about to stall (low Manifod pressure) so send more gas. You need to figure out which of the three it is. Explanation is crude but somewhat accurate.
You also need to make sure the IAC's are cycling. Take the cleaner off. Start it. Let it go to 1500. While you are at it disconnect the hose on the rear of the intake that feeds the headlights and plug it. You may have a leak in the headlight system. Also unplug the hose that goes to the master cyclinder and plug it at the manifold...the valve the hose attaches to at the master cylinder sometimes fails causing a vac leak. Anyway once its running. Give it a bit of gas...look down the hole to the driverside of the TBI's its right infront of where the IAC's screw in...do you see a pin moving in and out? You should this adjusts the air flow into the TBI's and are controlled by the ECM. I also assume you are plugging the hose that comes out of the rear TBI and goes to the aircleaner when you remove it.
Jim
